Japanese Language Stack Exchange is a question and answer site for students, teachers, and linguists wanting to discuss the finer points of the Japanese language. It's 100% free, no registration required.

I have noticed that some verbs have this "rare" or old form that is no longer used much (if at all). Here are some examples.

おそる： おそるべき者 → One who is feared

ほむ： ほむべきお方【かた】 → Seen often in my Japanese Bible describing God; "The one worthy of praise"

求【もと】む： 店員を求む → Help wanted

Were these forms prominently used at some point?

Why (and possibly, when) did their current forms (おそれる, ほめる, and 求める respectively) become the "standard" and overtake the older forms?

Are they used in other ways in modern Japanese, or only in fixed sayings/situations like these?

Can you list any other verbs like this? (I know this part is a little open-ended and thus is discouraged according to the site's acceptable questions, but if you know any, and answer the other questions above, throw it in with your answer)

2 Answers
2

Yes, they were predominately used in writing up until the end of World War II. Technically speaking, the movement to change the writing style to match the way people speak began in the early Meiji Era though. So, two writing styles existed for a long period of time.

Why (and possibly, when) did their current forms (おそれる, ほめる, and 求める respectively) become the "standard" and overtake the older forms?

After World War II, the government adopted a policy to use modern contemporary Japanese primarily based on the colloquial language used in Tokyo for literature.

Are they used in other ways in modern Japanese, or only in fixed sayings/situations like these?

The only remnants of literary language in modern Japanese are in the fixed sayings you see in your examples.

Can you list any other verbs like this? (I know this part is a little open-ended and thus is discouraged according to the site's acceptable questions, but if you know any, and answer the other questions above, throw it in with your answer)

If you search for "文語形 動詞", you should be able to find a bunch. Here is a link that lists a bunch from the dictionary.

These are classical verb forms. To be precise, the ones you have cited are all examples of the predicative form (終止形) of a -e/-u bigrade verb (下二段活用動詞). The predicative form became disused as early as the Muromachi period, and the modern form with -eru was predominant by the Edo period. (In fact, the spoken language of the Edo period is more or less where modern Japanese begins.) In written Japanese, classical grammar persisted until vernacularisation (言文一致) became widespread.

It's worth noting that 〜べき itself is a classical form, so it makes sense that it is used together with other classical forms. Rather oddly, 〜べき is one of a handful of auxiliaries which attach to the predicative form (except for r-stem irregular verbs (ラ行変格活用動詞) such as あり) in the traditional analysis. One example of this you may not even have noticed is すべき, which comes from the verb す (→ する).